1. Field of the Invention
The present invention relates to a fluorescent material of terbium aluminum garnet and producing methods therefor.
2. Description of Related Art
A typical white light-emitting diode (LED) includes a fluorescent material (or fluorescent agent, fluorescent gel, or phosphorescent layer) and an exciting light source. The exciting light source is a diode (such as a blue light-emitting diode) that emits an exciting light of an appropriate wavelength. The fluorescent material, when excited by the exciting light emitted by the exciting light source, emits an excited light of another color. The excited light and the exciting light emitted by the exciting light source mix with each other to generate a visible white light.
The fluorescent material is generally selected from crystalline compounds (or lattice of matrix crystal), such as terbium aluminum garnet (TAG, Tb3Al5O12). The TAG is usually used in applications of magneto-optical materials. Magneto-optical materials are optical information materials that have a magneto-optical effect in both the ultraviolet band and the infrared band. Utilizing magneto-optical characteristics of these materials as well as interaction and conversion between optics, electricity, and magnetism, these materials are processed to form magneto-optical devices providing optical modulation, optical isolation, optical illumination, optical inversion, optical information processing, and other optical/electrical/magnetic conversion.
Further, rare earth elements or other elements such as cerium (Ce), praseodymium (Pr), samarium (Sm), europium (Eu), gadolinium (Gd), dysprosium (Dy), holmium (Ho), erbium (Er), ytterbium (Yb), lutetium (Lu), strontium (Sr), yttrium (Y), vanadium (V), or chromium (Cr) can be added into the TAG to produce Tb3Al5O12:Ce3+ that includes an active center capable of transforming optical energy. Thus, the fluorescent materials when excited by an exciting light from an exciting light source, emits an excited light. The excited light and the exciting light mix with each other to generate a visible white light.
Although the fluorescent material of Tb3Al5O12:Ce3+ is widely used in manufacture of white light-emitting diodes, the brightness and the color evenness of the white light thus generated are unsatisfactory. In an attempt to overcome the above problems, the amount of cerium in the fluorescent materials can be adjusted, or the concentration and ingredients of the light-emitting center can be altered. However, adjustment and improvement in the brightness and color evenness are still very difficult, as there are many optional additives in the fluorescent material and as the chromatic coordinate of the fluorescent material covers a wide range.